Publications

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Journal Papers

  1. R. Carvajal, S. Ahmed, G.L. Nemhauser, K. Furman, V. Goel, Y. Shao. ‘‘Using diversification, communication and parallelism to solve mixed-integer linear programs,’’ to appear in Operations Research Letters, 2014. (preprint)

  2. Q. He, S. Ahmed and G.L. Nemhauser. ‘‘Minimum concave cost flow over a grid network,’’ to appear in Mathematical Programming, 2014. (preprint)

  3. F. Qiu, S. Ahmed, S.S. Dey, L. Wolsey. ‘‘Covering linear programming with violations,’’ to appear in INFORMS Journal on Computing, 2014. (preprint)

  4. B. Na, S. Ahmed, G.L. Nemhauser, J. Sokol. ‘‘A cutting and scheduling problem in float glass manufacturing,’’ to appear in Journal of Scheduling, 2014. (preprint)

  5. G. Angulo, S. Ahmed, S.S. Dey. ‘‘Semi-continuous network flow problems,’’ to appear in Mathematical Programming, 2014. (preprint)

  6. K. Bartlett, J. Lee, S. Ahmed, G.L. Nemhauser, J. Sokol, B. Na. ‘‘Congestion-aware dynamic routing in automated material handling systems’’, Computers and Industrial Engineering, vol. 70, pp. 176-182, 2014.

  7. M.J. Feizollahi, S. Ahmed, M. Modarres. ‘‘The robust redundancy allocation problem in series-parallel systems with budgeted uncertainty,’’ IEEE Transactions on Reliability, vol.63, pp.239-250, 2014.

  8. S. Ahmed. ‘‘Convex relaxations of chance constrained optimization problems,’’ Optimization Letters, vol.8, pp.1-12, 2014. (preprint)

  9. S. Ahmed. ‘‘A scenario decomposition algorithm for 0-1 stochastic programs,’’ Operations Research Letters, vol. 41, pp. 565-569, 2013. (preprint)

  10. B. Na, S. Ahmed, G.L. Nemhauser, J. Sokol. ‘‘Optimization of automated float glass lines,’’ International Journal of Production Economics (Special issue on Cutting and Packing), vol.145, pp. 561-572, 2013. (preprint)

  11. A. Gupte, S. Ahmed, M.-S. Cheon, and S.S. Dey. ‘‘Solving mixed integer bilinear problems using MIP formulations,’’ SIAM Journal on Optimization, vol.23, pp.721-744, 2013. (preprint)

  12. S. Ahmed and D.J. Papageorgiou. ‘‘Probabilistic set covering with correlations,’’ Operations Research, vol.61, pp.438-452, 2013. (preprint)

  13. N. Kong, A.J. Schaefer, and S. Ahmed. ‘‘Totally unimodular stochastic programs,’’ Mathematical Programming, vol.138, pp.1-13, 2013.

  14. J.P. Vielma, S. Ahmed, and G.L. Nemhauser. ‘‘Mixed integer linear programming formulations for probabilistic constraints,’’ Operations Research Letters, vol.40, pp.153-158, 2012. (preprint)

  15. Q. He, S. Ahmed, and G.L. Nemhauser. ‘‘Sell or hold: A simple two-stage stochastic combinatorial optimization problem,’’ Operations Research Letters, vol.40, pp.69-73, 2012. (preprint)

  16. Q. He, S. Ahmed, and G.L. Nemhauser. ‘‘A probabilistic comparison of split and type 1 triangle cuts for two row mixed-integer programs,’’ SIAM Journal on Optimization, vol.21, pp.617-632, 2011. (preprint)

  17. S. Ahmed and A. Atamturk. ‘‘Maximizing a class of submodular utility functions,’’ Mathematical Programming, vol.128, pp.149-169, 2011 (preprint)

  18. S. Shen, J.C. Smith, and S. Ahmed. ‘‘Expectation and chance-constrained models and algorithms for insuring critical paths,’’ Management Science, vol.56, pp.1794-1814, 2010.(e-print)

  19. J.P. Vielma, S. Ahmed, and G.L. Nemhauser. ‘‘A note on: 'A superior representation method for piecewise linear functions’ by Li, Lu, Huang and Hu,’’ INFORMS Journal on Computing, vol.22, pp.493-497, 2010. (preprint)

  20. S. Ahmed, O. Gozbasi, M. Savelsbergh, I. Crocker, T. Fox, and E. Schreibmann. ‘‘An automated Intensity-Modulated Radiation Therapy planning system,’’ INFORMS Journal on Computing, vol.22, pp.568-583, 2010. (preprint)

  21. J.P. Vielma, S. Ahmed and G.L. Nemhauser. ‘‘Mixed-integer models for nonseparable piecewise linear optimization: Unifying framework and extensions,’’ Operations Research, vol.58, pp.303-315, 2010. (preprint)

  22. K. Huang and S. Ahmed. ‘‘A stochastic programming approach for planning horizons of infinite horizon capacity planning problems,’’ European Journal of Operational Research, vol.200, pp.74-84, 2010.

  23. J. Luedtke, S. Ahmed and G.L. Nemhauser. ‘‘An integer programming approach for linear programs with probabilistic constraints,’’ Mathematical Programming, vol.122, pp.247, 2010 (preprint)

  24. Z.C. Taskin, J.C. Smith, S. Ahmed, and A.J, Schaefer. ‘‘Cutting plane algorithms for solving a robust edge-partition problem,’’ Discrete Optimization, vol.6, pp.420-435, 2009.

  25. F. Kilinc-Karzan, A. Toriello, S. Ahmed, G.L. Nemhauser, and M. Savelsbergh. ‘‘Approximating the stability region for binary mixed-integer programs,’’ Operations Research Letters, vol.37, pp.250-254, 2009 (preprint)

  26. P. Schutz, A. Tomasgard and S. Ahmed. ‘‘Supply chain design under uncertainty using sample average approximation and dual decomposition,’’ European Journal of Operational Research, vol.199, pp.409-419, 2009.

  27. B. Pagnoncelli, S. Ahmed, and A. Shapiro. ‘‘The sample average approximation method for chance constrained programming: theory and applications,’’ Journal of Optimization theory and Applications, vol.142, pp.399-416, 2009 (preprint)

  28. K. Huang and S. Ahmed. ‘‘The value of multi-stage stochastic programming in capacity planning under uncertainty,’’ Operations Research, vol.57, pp.893-904, 2009 (preprint)

  29. Y. Guan, S. Ahmed and G.L. Nemhauser. ‘‘Cutting planes for multi-stage stochastic integer programs,’’ Operations Research, vol.57, pp.287-298, 2009 (preprint)

  30. S. Ahmed, D. Filipovic, and G. Svindland. ‘‘A note on natural risk statistics,’’ Operations Research Letters, vol.36, pp.662-664, 2008 (preprint)

  31. J. Luedtke and S. Ahmed. ‘‘A sample approximation approach for optimization with probabilistic constraints,’’ SIAM Journal on Optimization, vol.19, pp.674-699, 2008 (preprint)

  32. W. Wang and S. Ahmed. ‘‘Sample average approximation of expected value constrained stochastic programs,’’ Operations Research Letters, vol.36, pp.515-519, 2008 (preprint)

  33. J.P. Vielma, S. Ahmed and G.L. Nemhauser. ‘‘A lifted linear programming branch-and-bound algorithm for mixed integer conic quadratic programs,’’ INFORMS Journal on Computing, vol.20, pp.438-450, 2008 (preprint)

  34. K. Huang and S. Ahmed. ‘‘On a multi-stage stochastic programming model for inventory planning,’’ Information Systems and Operational Research, vol. 46, pp. 155-163, 2008.

  35. S. Ahmed and N. V. Sahinidis. ‘‘Selection, acquisition, and allocation of manufacturing technology in a multi-product environment,’’ European Journal of Operational Research, vol. 189, pp. 807-821, 2008.

  36. S. Ahmed, U. Cakmak and A. Shapiro. ‘‘Coherent risk measures in inventory problems,’’ European Journal of Operational Research, vol.182, pp.226-238, 2007 (preprint)

  37. Y. Guan, S. Ahmed and G. L. Nemhauser. ‘‘Sequential pairing of mixed integer inequalities,’’ Discrete Optimization, vol.4, pp.21-39, 2007 (preprint)

  38. S. Ahmed. ‘‘Convexity and decomposition of mean-risk stochastic programs ,’’ Mathematical Programming, vol.106, pp.433-446, 2006 (preprint)

  39. Y. Guan, S. Ahmed, A. J. Miller, and G. L. Nemhauser. ‘‘On formulations of the stochastic uncapacitated lot-sizing problem,’’ Operations Research Letters, vol.34, pp.241-250, 2006.

  40. M.-S. Cheon, S. Ahmed and F. Al-Khayyal. ‘‘A branch-reduce-cut algorithm for the global optimization of probabilistically constrained linear programs,’’ Mathematical Programming, vol.108, pp.617-634, 2006 (preprint)

  41. Y. Guan, S. Ahmed, G.L. Nemhauser and A.J. Miller. ‘‘A branch-and-cut algorithm for the stochastic uncapacitated lot-sizing problem,’’ Mathematical Programming, vol.105, pp.55-84, 2006 (preprint)

  42. S. Ahmed and Y. Guan. ‘‘The Inverse Optimal Value Problem,’’ Mathematical Programming, vol.102, pp.91-110, 2005 (preprint)

  43. T. Santoso, S. Ahmed, M. Goetschalckx, and A. Shapiro. ‘‘A stochastic programming approach for supply chain network design under uncertainty,’’ European Journal of Operational Research, vol.167, pp.96-115, 2005 (preprint)

  44. A. Shapiro and S. Ahmed. ‘‘On a class of minimax stochastic programs,’’ SIAM Journal on Optimization, vol.14, pp.1237-1249, 2004 (preprint)

  45. S. Ahmed, M. Tawarmalani, and N. V. Sahinidis. ‘‘A finite branch and bound algorithm for two-stage stochastic integer programs,’’ Mathematical Programming, vol.100, pp.355-377, 2004 (preprint)

  46. S. Takriti and S. Ahmed. ‘‘On Robust Optimization of Two-Stage Systems,’’ Mathematical Programming, vol.99, pp.109-126, 2004 (preprint)

  47. G. Parija, S. Ahmed, and A. J. King. ‘‘On bridging the gap between stochastic integer programming and mixed-integer solver technologies,’’ INFORMS Journal on Computing, vol.16, 2004 (preprint)

  48. S. Ahmed and R. Garcia. ‘‘Dynamic capacity acquisition and assignment under uncertainty,’’ Annals of Operations Research, vol.124, pp. 267-283, 2003 (preprint)

  49. B. Verweij, S. Ahmed, A. J. Kleywegt, G. Nemhauser, and A. Shapiro. ‘‘The sample average approximation method applied to stochastic routing problems: A computational study,’’ Computational and Applied Optimization, vol.24, pp.289-333, 2003 (preprint)

  50. S. Ahmed and N. V. Sahinidis. ‘‘An Approximation Scheme for Stochastic Integer Programs Arising in Capacity Expansion,’’ Operations Research, vol.51, pp.461-471, 2003 (preprint)

  51. S. Ahmed, A. J. King, and G. Parija. ‘‘A Multi-Stage Stochastic Integer Programming Approach for Capacity Expansion under Uncertainty,’’ Journal of Global Optimization, vol. 26, pp.3-24, 2003 (preprint)

  52. M. Tawarmalani, S. Ahmed, and N. V. Sahinidis. ‘‘Product disaggregation and relaxations of mixed-integer rational programs,’’ Optimization and Engineering, vol.3, pp. 281-303, 2002.

  53. M. Tawarmalani, S. Ahmed, and N. V. Sahinidis. ‘‘Global optimization of 0-1 hyperbolic programs,’’ Journal of Global Optimization, vol. 24, pp. 385-417, 2002.

  54. S. Ahmed and N. V. Sahinidis. ‘‘Analytical investigations of the process planning problem,’’ Computers & Chemical Engineering, vol. 23, pp. 1605-1621, 2000.

  55. S. Ahmed, N. V. Sahinidis, and E. N. Pistikopoulos. ‘‘An improved decomposition algorithm for process planning under uncertainty,’’ Computers & Chemical Engineering, vol. 23, pp. 1589-1604, 2000.

  56. S. Ahmed and N. V. Sahinidis. ‘‘Robust process planning under uncertainty,’’ Industrial & Engineering Chemistry Research, vol. 37, pp. 1883-1892, 1998.

Book Chapters

  1. S. Ahmed. ‘‘Two stage stochastic integer programming,’’ in the Encylopedia of Optimization (T. Choran (Ed.)), Wiley, 2010. (preprint)

  2. S. Ahmed and A. Shapiro. ‘‘Solving chance-constrained stochastic programs via sampling and integer programming,’’ in Tutorials in Operations Research, Z.-L. Chen and S. Raghavan (eds.), INFORMS, 2008. (preprint)

  3. M. Goetschalckx, S. Ahmed, A. Shapiro, and T. Santoso. ‘‘Strategic design of robust global supply chains under uncertainty,” in Progress in Material Handling Research: 2004, R. Meller et al. (eds.), The Material Handling Institute, NC, pp. 103-117, 2004.

  4. S. Ahmed and N. V. Sahinidis. ‘‘Techniques in long range planning of chemical manufacturing systems,’’ in Computer-Aided Design, Engineering, and Manufacturing: Systems Techniques and Applications, Volume V: The Design of Manufacturing Systems, C. T. Leondes (ed.), CRC Press LLC, Boca Raton, FL, pp.1-25, 2001.

  5. S. Ahmed and N. V. Sahinidis. ‘‘Chemical process planning,’’ in The Encyclopedia of Optimization, C. A. Floudas and P. M. Pardalos (eds.), Kluwer Academic Publishers, Vol.1, pp.246-252, 2001.

Conference Proceedings

  1. J. Luedtke, S. Ahmed and G.L. Nemhauser. ‘‘An integer programming approach for linear programs with probabilistic constraints,’’ in Proceedings of the 12th International Integer Programming and Combinatorial Optimization (IPCO) Conference, Lecture Notes in Computer Science, pp. 310-423, 2007.

  2. Y. Guan, S. Ahmed and G. L. Nemhauser. ‘‘Sequential pairing of mixed integer inequalities,’’ in Proceedings of the 11th International Integer Programming and Combinatorial Optimization (IPCO) Conference, Lecture Notes in Computer Science, pp. 23-34, 2005.

  3. S. Ahmed. ‘‘Semiconductor tool planning via multi-stage stochastic programming,’’ Proceedings of the International Conference on Modeling and Analysis in Semiconductor Manufacturing, Mackulak et al. (eds.), pp. 153-157, 2002.

Working Papers and Technical Reports

  1. S. Ahmed, Q. He, S. Li, G.L. Nemhauser. ‘‘Minimum concave cost flows in capaciated grid networks,’’ submitted 2014.

  2. F. Qiu, S. Ahmed, S.S. Dey. ‘‘Strengthened bounds for the probability of k-out-of-n events,’’ submitted 2013.

  3. G. Angulo, S. Ahmed, S.S. Dey, V. Kaibel. ‘‘Forbidden vertices,’’ submitted 2013.

  4. A. Gupte, S. Ahmed, M.-S. Cheon, S.S. Dey. ‘‘Pooling problems: Relaxations and discretizations,’’ submitted 2013.

  5. S. Ahmed, J. Yu. ‘‘Approximating the expected utility knapsack problem,’’ ISyE Technical Report 2012.

  6. S. Ahmed. ‘‘Smooth minimization of two-stage stochastic linear programs,’’ ISyE Technical Report 2006.

  7. A. Parmar, S. Ahmed, J. Sokol. ‘‘An integer programming approach to the OSPF weight setting problem,’’ ISyE Technical Report 2006.

  8. S. Ahmed. ‘‘Mean-risk objectives in stochastic programming,’’ ISyE Technical Report 2004.

  9. S. Ahmed and A. Shapiro. ‘‘The sample average approximation method for stochastic programs with integer recourse,’’ ISyE Technical Report, 2002.

  10. S. Takriti and S. Ahmed. ‘‘Managing short-term electricity contracts under uncertainty: A minimax approach,’’ ISyE Technical Report, 2002.

  11. S. Ahmed and M. A. Haque. ‘‘Multi-facility retail locationing using p-choice models,’’ ISyE Technical Report, 2001.

  12. A. J. King, S. Takriti, and S. Ahmed. ‘‘Issues in risk modeling for multi-stage systems,’’ IBM Research Report No. RC-20993, 1997.